One of the most rapidly increasing groups of human immunodeficiency virus (HIV) infected patients are infants and children with perinatally acquired infection. Central nervous system dysfunction has been found in almost 90% of these patients with symptomatic HIV infection. Although the neurologic manifestations of HIV infection have been reported in several series, these clinical studies have dealt with children identified only after symptoms of HIV infection have developed. At the present time, insufficient information is available to predict which children with HIV infection will develop a static or progressive encephalopathy. In addition, prospective longitudinal studies are necessary to determine (1) the natural history of brain involvement in congenitally acquired HIV infection (2) determinants predictive of AIDS dementia, and (3) the variability in both disease expression and pathologic changes in demented patients. In this study, infants born to HIV seropositive mothers will be followed prospectively from birth to determine the natural history of AIDS dementia by using a standardized series of (1) neurologic, developmental and validated psychological examinations, (2) neurologic tests including neuroimaging and neurophysiologic studies, and (3) immunologic studies of serum and cerebral spinal fluid. Ninety infants enrolled over three years will be followed from birth over a five year period. It is estimated that of this group, 15 infants per year will develop HIV infection and the remainder will serve as a control group. The study will determine whether clinical and laboratory testing can detect central nervous system involvement in neurologically asymptomatic infants and elucidate the determinants predictive of progressive encephalopathy associated with HIV infection. The results of this study will (1) allow for earlier diagnosis of CNS involvement, and (2) provide a framework for the rational selection of patients who might benefit from new therapeutic approaches before irreversible CNS dysfunction has occurred. This clinical study will provide the foundation for collaboration with immunologic, virologic, and pathologic studies to address issues of pathogenesis.